Headlight lamp



Jun 18, 1935. F. MAYO 2,005,194

HEADLIGHT LAMP Filed Dec. 1, 1952 Patented June 18, 1935 PATENT OFFICE HEADLIGHT LAMP Franklin Mayo,

Chicago, Ill., assignor to Walter Armstrong, Chicago, 111. Application December 1, 1932, Serial No. 845,251 1 Claim. (Cl. 176-28) My invention relates to lamps for headlights and more especially to lamp bulbs used in automobile headlights and the relation between the lamp bulb and the reflector of the headlight.

The object of my invention is to eliminate the objectionable glare of "bright lights" without detracting from the proper illumination of those regions which require illumination, and on the contrary in the course of the elimination of the glare distributing the illumination more advantageously.

The bulb of my invention is applicable to the standard parabolic type of reflector in common use, and requires no change over the standard 1 equipment except for the substitution of my lamp bulbs for the ordinary lamp bulbs.

I employ a reflecting surface on the bulb. In

previous proposals to employ reflecting surfaces on the bulbs, when the reflecting surface has been concave there has been a tendency to reflect the light back to the filament or at least to the interior of the bulb, with the result that the bulb becomes excessively hot and the life of the lamp is shortened. When the reflecting surface has been convex, there has been a twofold objection. One is that the reflecting surface comes dangerously near the heat of the filament if most advantageously placed. The other is that the curved surface has been so arranged that light so reflected by it is discharged from the headlight as a substantially parallel beam tending to give a uniform distribution of light. redistribute the discharged light so that instead of the merely parallel beam and the more or less asuniform divergent beam surrounding it, I provide ample illumination in various regions as required by those regions. More specifically, I provide additional illumination for the foreground of the road whereby the driver can see 40 ruts and small objects not visible at a distance. I provide additional side illumination in a more concentrated form than usual which enables the driver readily to read the traffic signs at the road sides and also to illuminate the road ahead when turning corners. At the same time I give the main and more or less parallel beam light a slight downward tilt without downwardly'tilting the blind spot where the direct glare is blocked Out.

I accomplish these objects preferably by a reflecting surface on the end of thebulb which is conical with its apex toward the filament. However the reflecting surface is well removed from the filament, so that it is not in danger of being By my invention 1.

aflected by the heat of the filament. The reflecting surface at the end of the bulb cannot reflect heat back toward the filament or even toward the base of the bulb.

Further to accomplish these objects, I preferably tilt the axis of the conical reflecting surface out of coincidence with the axis of the headlight reflector. A further feature of my invention is that I effect this angular relation between the main reflector and the conical reflector of the bulb without the necessity 'of special adjustment or change of the lamp socket. Instead I use a standard lamp socket. When inserted in the socket, the lamp base is aligned with the axis of the main reflector; and I position the bulb so that it stands at a slight angle to the axis of the base.

My invention is applicable to multi-fllament types of bulbs. Most of the advantages of my bulb are retained when only an auxiliary or "dim filament is lighted.

Thus from the user's standpoint, the bulb of my invention, as compared with an ordinary bulb of the same candle power, eliminates the objectionable glare to on-coming drivers while, due to the economical redistribution of light, it gives more effective illumination. In fact, because oi the elimination of the glare by my invention, I am enabled to use lamps of greater candle power than have heretofore been practicable, because heretofore the glare has been a limiting factor in the candle power which can be used in headlights.

The foregoing together with further objects, features and advantages of my invention are set forth in the following description of a specific embodiment thereof and illustrated in the accompanying drawing, wherein:

Fig. 1 is a top plan view of a lamp bulb for an automobile headlight embodying my invention;

Fig. 2 is a side elevation, the bulb being broken into vertical, longitudinal cross section; and

Fig. 3 is a diagrammatic view showing the bulb positioned in the reflector. of a standard automobile headlight. 5

The lamp bulb has a base iii of substantially standard construction with a shell ll, rear contacts l2 and I3 and bayonet pins ii. The bulb l5, however, is preferably of cylindrical contour. It is so disposed that its axis is at an angle a of about four degrees to the axis of the base, the two axes intersecting at the outer end of the base. This angular displacement of the axes occurs only in a vertical plane; in plan they are coincident,

as indicated in Fig. l. s

Preferably the outer end of the base shell II is cut obliquely as shown in Fig. 2 whereby it more snugly fits the neck of the bulb l5 and thereby more adequately protects it and facilitates assembly.

The bulb contains the customary glass stem l6 and three lead-in wires supporting the primary filament l1 and the secondary filament ii. The secondary filament II, which is thrown into circuit in substitution of the primary filament H for city driving, may be of equal wattage with the primary filament or of a lesser wattage.

As customary, each U-shaped filament is disposed in a horizontal rather than a vertical plane so that the bulk of the direct and reflected light will be cast downward or upward rather than sidewise.

Preferably the primary filament I! is positioned on the axis of the bulb. This brings it slightly above the axis of the base. As the standard socket aligns the base with the axis of the reflector, the primary filament l1 comes slightly above the axis of the reflector. Longitudinally, the filament is positioned the standard distance from the base bayonet pins H. The primary filament I! is thus positioned slightly above the focal point I of the usual parabolic reflector is. The auxiliary filament I8 is thus positioned still further above the focal point.

The outer end of the bulb I5 is in the form of an inwardly pointing cone concentric with the axis of the bulb and silvered on its outer side to provide a conical reflecting surface 20. The apex of the cone comes at a considerable distance from the filaments.

Referring now to Fig. 3, for the operation of my lamp bulb when it is installed in a standard reflector, I shall first discuss the direct or nonrefiected rays emanating from the primary fllament. They are limited peripherally by the outer edge of the reflector and centrally by the reflecting cone, leaving an annular band designated at the top by d and at the bottom by 11'. Because of the slightly elevated position of the conical re flector, the angle d is substantially less than the angle d, with the result that the latter discharges the greater part of the direct rays on to the foreground of the road, a lesser amount to the roadside and the least amount upwardly.

The bulk of the light emanating from the fllament is that passing directly to the headlight reflector and reflected forwardly as a substantially parallel beam. This main beam designated above the center as r and below the center as r' has a dark spot at the center blocked out by the conical reflector. This dark spot is doubly dark because the conical reflector intercepts not only the direct rays but the main reflector rays which would otherwise pass through the central region. Because the primary filament I! is slightly above the focal point of the reflector IS, the main beam r, r' is given a slight downward tilt, whereby it is not necessary to tilt the axis of the headlight itself. However, the fact that the conical reflector is set slightly higher than the main filament l1 ttends to offset a corresponding tilting of the dark spot, with a result that the dark spot is substantially in alignment with the vision of an on-coming motorist.

A third class of rays are those which strike the reflecting surface of the cone and are reflected to the main reflector l9 and in turn reflected outwardly as an annular band. These rays are indicated in Fig. 3 at the top as c and at the bottom as c. They are discharged from the main reflector with a decided inclination toward the axis. They cross substantially at the axis, the ray c going down to illuminate the foreground of the road forwardly of the rays d, and the rays c passing upwardly. As regards degrees of original emanation of light from the primary filament II, the beams c and c are equal. But the beam c is projected forwardly by the reflecting surfaces as a more concentrated beam while the beam 0' is more diflused. This is of distinct advantage. The region toward which the beam 0 passes is one requiring only very general illumination which is best served by the dissipation of the beam over a large region. On the other hand the foreground of the road, which is served by the concentrated beam 0 requires more concentrated light. The concentrated beam 0 is calculated to fall on the foreground of the road at that region where the average motorist can best see and recognize ruts, stones, small animals, traffic directions and warnings painted on the pavement, and the like.

In'connection with the diagram of Fig. 3, I have discussed only the vertical aspects of the operation of my headlight bulb. I shall now discuss the operation of my headlight bulb as regards the horizontal distribution of the light. The angular displacement, in a vertical plane, of the axis of the cone and the primary filament II from the axis of the main reflector causes the differences between the upper direct beam (1 and the lower direct beam d and between the upper cone-reflected beam 0 and the lower beam 0'. It also causes the downward tilting of the main beam r, r. When considered in horizontal section, however, the lamp of my invention and the main reflector I 9 cause no such differences. This is because in plan section the axis of the bulb on which the reflecting cone and the primary filament I! are centered, is coincident with the axis of the reflector. The beam corresponding to'c, c' is equally divided as between the right and left .side. Similarly, the direct beam corresponding to d, d is equalized as between right and left. The main reflected beam r, 1- has no deflection, but is projected straight ahead. One or both of the headlights may if desired be turned about the vertical axis by the usual adjustment to give a slight divergence toward the side of the road. However, this is by no means necessary as the several classes of rays thrown by the headlight are ample to provide for the needs. The direct rays corresponding to d, d then give general side illumination over an arc of considerable magnitude. The main beams corresponding to r, 7" continue to provide the primary illumination as in the ordinary headlight. The beams corresponding to c and c' continue to cross and are projected to opposite sides of the road. These beams diverge more than the main reflector beams, but on the other hand are not so diffused or calculated to cover so large a region as the direct rays corresponding to d, d. The concentration of light thus reflected to the sides of the road by the conical reflector and the angle at which it is reflected are calculated to make visible traflic and road signs at the side of the road at a distance which is close enough to be read and still far enough to give the motorist the necessary time to act upon them. This largely eliminates the difllculty so often encountered by motorists in either going past road signs without being able to read them at all or having to wait until the signs are reached before they become legible, leaving the motorist with inadequate time to act in accordance with them. If a motorist is unable tosee or read a stop sign, danger sign, curve sign or the like in time, serious injury is likely to result. If he cannot read a route number or route turn arrow at an intersection at the proper time, the motorist is subjected to the inconvenience and danger of having to back up or turn around. The widely divergent general illumination provided angularly beyond the parallel beam from the main reflector in the ordinary headlight is inadequate to meet this requirement unless it be at the expense of economy of current consumed,

I have discussed the operation of my headlight bulb when using the primary filament l'l. When the filament I8 is used instead of the filament II, the increased elevation of the filament above .the focal point of the reflector l9 causes a greatly accentuated downward tilt of the various classes of rays. The main reflector rays 1, r are tilted downwardly sufllciently that they all come under the eyes of an on-coming driver. The direct rays d are projected at a slightly lower angle, but not such as will meet'the eyes of another driver. The lower direct rays d are slightly more concentrated on the immediate foreground of the road. Of rays reflected by the conical reflector, but very few will pass from the filament l8 to the underside of the cone, with the result that the rays 0' become more or less negligible. On theother hand, the rays 0 are greatly increased and re-- flected at still more of a downward inclination. As a result the intense illumination of the foreground by the rays 0 is increased and the rays fall upon the road nearer the vehicle. This is consistent with the speed of the vehicle being reduced as is generally the case when the auxiliary filament is used. The side illumination of the road is not materially affected by the use of the upper or auxiliary filament I8, except that the rays in general are slightly lowered.

It will be observed in general that the light reflected by the conical reflector does not pass direflected directly out of the headlight it would be a relatively useless peripheral band of light. All of the rays emanating from the filament and striking the cone reflector are reflected with some forward component, with the result that heat is continually moved forward by the conical reflector and does not reflect the heat toward the rear end of the main reflector nor toward the filament or base of the bulb. This control of the heat problem insures less damage to the bulb and the inner surfaces of the main reflector which might otherwise be adversely affected by the intense heat. The conical reflector is set well out from the flla ment. Heat absorbed by the reflector is thus less, and the conical form of the reflector is one which tends to conduct away, spread and dissipate the heat most effectively.

While I have described this specific embodiment of my invention I contemplate that changes may be made therein without departing from the scope or spirit of my invention.

I claim: A headlight lamp for mounting in a standard horizontally disposed socket of a parabolic reflector-type automobile headlight, comprising a lamp base constructed and arranged to be received and aligned by said socket, a lamp bulb supported at one end in the base, primary and secondary filaments mounted within the bulb in spaced relation to one side of the axis of the base, and a conical reflector at the outer end of the bulb and flxedly supported by the bulb with its axis disposed at an angle to the axis of the base and concentric with the primary filament of the bulb, where- 'by all of the light emanating from the filament will be reflected as a cone to the parabolic reflector from which the greater part will be projected to the foreground, a. lesser amount to the sides, and the least amount upwardly.

MAYO. 

